package com.chinathinks.core.net;

import java.io.IOException;
import java.util.Date;
import java.io.DataInputStream;

/***
 * The TimeTCPClient class is a TCP implementation of a client for the Time
 * protocol described in RFC 868. To use the class, merely establish a
 * connection with {@link org.apache.commons.net.SocketClient#connect connect }
 * and call either {@link #getTime getTime() } or {@link #getDate getDate() } to
 * retrieve the time, then call
 * {@link org.apache.commons.net.SocketClient#disconnect disconnect } to close
 * the connection properly.
 * <p>
 * <p>
 * 
 * @author Daniel F. Savarese
 * @see TimeUDPClient
 ***/

public final class TimeTCPClient extends SocketClient {
	/*** The default time port. It is set to 37 according to RFC 868. ***/
	public static final int DEFAULT_PORT = 37;

	/***
	 * The number of seconds between 00:00 1 January 1900 and 00:00 1 January
	 * 1970. This value can be useful for converting time values to other
	 * formats.
	 ***/
	public static final long SECONDS_1900_TO_1970 = 2208988800L;

	/***
	 * The default TimeTCPClient constructor. It merely sets the default port to
	 * <code> DEFAULT_PORT </code>.
	 ***/
	public TimeTCPClient() {
		setDefaultPort(DEFAULT_PORT);
	}

	/***
	 * Retrieves the time from the server and returns it. The time is the number
	 * of seconds since 00:00 (midnight) 1 January 1900 GMT, as specified by RFC
	 * 868. This method reads the raw 32-bit big-endian unsigned integer from
	 * the server, converts it to a Java long, and returns the value.
	 * <p>
	 * The server will have closed the connection at this point, so you should
	 * call {@link org.apache.commons.net.SocketClient#disconnect disconnect }
	 * after calling this method. To retrieve another time, you must initiate
	 * another connection with
	 * {@link org.apache.commons.net.SocketClient#connect connect } before
	 * calling <code> getTime() </code> again.
	 * <p>
	 * 
	 * @return The time value retrieved from the server.
	 * @exception IOException
	 *                If an error occurs while fetching the time.
	 ***/
	public long getTime() throws IOException {
		DataInputStream input;
		input = new DataInputStream(_input_);
		return (long) (input.readInt() & 0xffffffffL);
	}

	/***
	 * Retrieves the time from the server and returns a Java Date containing the
	 * time converted to the local timezone.
	 * <p>
	 * The server will have closed the connection at this point, so you should
	 * call {@link org.apache.commons.net.SocketClient#disconnect disconnect }
	 * after calling this method. To retrieve another time, you must initiate
	 * another connection with
	 * {@link org.apache.commons.net.SocketClient#connect connect } before
	 * calling <code> getDate() </code> again.
	 * <p>
	 * 
	 * @return A Date value containing the time retrieved from the server
	 *         converted to the local timezone.
	 * @exception IOException
	 *                If an error occurs while fetching the time.
	 ***/
	public Date getDate() throws IOException {
		return new Date((getTime() - SECONDS_1900_TO_1970) * 1000L);
	}

}
